Verification of the seismic P-wave velocities under Moho boundary: Central Poland case study, LUMP profile
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The tectonic settings investigated by several seismic projects in previous research targeting the structure in Central Poland mainly focused on the Earth’s crust. In this paper, we present P-wave velocity verifcation in the uppermost mantle beneath LUMP profle towards SSE-NNW. Using recordings of 36 DATA-CUBE recorders from ca. 300–490 km far earthquake in coal mine “Janina” in southern Poland, we calculated travel times to verify P-wave velocity below the Moho boundary from previous studies. It shows that a signifcantly lower mean velocity value should be used for the upper mantle while counting these ofsets of travel times in the SSE-NNW direction than that used on previous profles. We present two possible models: frst, the most simple one that fts the observed frst arrivals, and the second with a low-velocity layer beneath the Moho boundary. In both cases, we used a priori crustal model focusing only on P-wave velocity in the uppermost mantle. Both of them signifcantly improved adjustment of travel times to the observed data. To evaluate the tendency of adopting too high velocities beneath the Moho, we used also 11 broadband stations, Reftek 151-121 “Observer”, from “13 BB Star” passive experiment and 6 STS-2 seismometers from permanent stations of the Polish Seismological Network (PLSN).